What is your local dual enrollment situation like where she will presumably re-enroll eventually?
Are there a lot of offerings? Is it hard to get permission?
What does the future of that program look like in the next four years? Which way is the wind blowing-- is it likely that the program could get axed via Common Core implementation?
All of those things would play into that decision for me.
If she's still bored NOW, after a 1y skip, then effectively UN-doing that skip seems unwise without having some kind of plan hammered out ahead of time with the high school. Will they allow her to skip some graduation requirements in favor of dual enrollment? If so, get that in writing.
Personally, I'd be more likely to call her a 7th grader for now, and see where you're at in another year. If nothing else, you can always hit "un-do" on the skip when you go to actually ENROLL her in what they consider to be 10th grade. Just tell them that you've been unschooling and therefore, she's a 9th grader.
Or tell them that she is a 10th grader.
Whatever seems to align better with your goals at that time. KWIM?